1. Field of the Invention
The present invention relates to an apparatus to couple laser radiation into a microwave waveguide or other microwave structure.
2. Description of the Prior Art
For uranium isotope separation, a laser wavelength for isotope-selective excitation is required which cannot be set with the required precision using fixed frequency lasers known in the prior art.
The prior art includes electrooptic modulation, a method by means of which the desired wavelengths can be produced utilizing frequency shift principles. If the required modulation frequencies are in the microwave range, it is necessary to incorporate an electrooptic modulator crystal into a microwave waveguide, so that the laser beam and modulating microwave can pass through the electrooptic modulator crystal substantially colinearly. Using this method, it is difficult to couple the laser radiation into the microwave waveguide.
Devices known in the prior art couple a laser beam by means of a hole provided in a microwave elbow [See, for example, Appl. Phys. Lett. 34(7), Apr. 1, 1979, Page 452, FIG. 1. This prior art publication is hereby expressly incorporated by reference as if the entire contents thereof were fully set forth herein.] Using this method, this hole may have only small dimensions, as compared to the dimensions of the hollow conductor, in order not to interfere with the microwave mode and in order to prevent undesirable reflection.
This means that the laser beam must be focused through the provided coupling hole. With the energies required for an industrial process, this produces problems with breakdowns and arcing in the vicinity of the coupling hole. Moreover, it is difficult to adjust the laser beam to the geometry of the microwave waveguide, in order that the beam will illuminate, as much as possible, the cross sectional area of the electrooptic crystal. This is necessary, however, to obtain a high degree of efficiency with simultaneously high laser power.
Examples of issued U.S. patents which generally discuss the modulation of laser radiation with microwave radiation are U.S. Pat. No. 4,208,091, issued June 17, 1980 and entitled "Broadband Microwave Waveguide Modulator for Infrared Lasers" and U.S. Pat. No. 4,118,676, issued Oct. 3, 1978 and entitled "Method and Apparatus for Driving an Optical Waveguide with Coherent Radiation", both of these issued U.S. patents being hereby expressly incorporated by references as if the entire contents thereof were fully set forth herein.